gfortran in Ubuntu images broken because of added -gdwarf-5 flag

[rgommers]

Description

Today all Ubuntu jobs in the SciPy CI on Azure DevOps started breaking because gfortran is no longer able to compile anything. The way this shows up is:

as: unrecognized option '--gdwarf-5'
/home/linuxbrew/.linuxbrew/bin/gfortran -Wall -g -ffixed-form -fno-second-underscore -Wall -g -fno-second-underscore -fPIC

We are not installing Linuxbrew explicitly, nor are adding a -gdwarf-5 flag. This is likely to be a mixup in GCC specs caused by gh-6258.

See scipy/scipy#17058 for more details on the SciPy build failures in CI.

Platforms affected

• Azure DevOps
• GitHub Actions

Runner images affected

• Ubuntu 18.04
• Ubuntu 20.04
• Ubuntu 22.04
• macOS 10.15
• macOS 11
• macOS 12
• Windows Server 2019
• Windows Server 2022

Image version and build link

I'll note that the Ubuntu 22.04 image should also be affected, however we don't have any CI jobs using that image so I can't be sure that it is affected.

Images affected:

Image: ubuntu-20.04
Version: 20220919.1

Image: ubuntu-18.04
Version: 20220919.2

Is it regression?

Yes. The problem started about 6 hours ago. The previous image was 20220905.1, that worked fine.

Expected behavior

gfortran should not be passed a flag -gdwarf-5, and compiling Fortran code with gfortran should work.

Actual behavior

See issue description.

Repro steps

Here is a CI job that fails: https://github.com/scipy/scipy/blob/main/azure-pipelines.yml#L58.

Compiling any Fortran code with gfortran -g should reproduce the issue.

[al-cheb]

Hey @rgommers.
We will take a look at it.

[dawidd6]

Ubuntu 22.04 should not be affected as Homebrew does not need to install newer gcc there.

[mikhailkoliada]

gfortran symlink removed, changes will be released this week.

[rgommers]

Thanks @mikhailkoliada! It looks like in the meantime the default image got reverted to an older build, so our CI is working again.

[mikhailkoliada]

homebrew has been removed from $PATH so it will not affect you anymore (though we still remove gfortran symlink too, so if you add homebrew back to PATH it should work too).